In known mixers of this type the mixing tools are arranged at the ends of the radial arms of the mixing mechanism in such a way that they revolve close to the internal wall of the container and are thus immersed completely in the product being mixed, particularly if the mixer is operated with a high degree of filling. If the mixing mechanism is operated at a relatively low speed most of the product to be mixed lies in the lower region of the container and the individual mixing tools have to run submerged through a pile of product being mixed. The individual mixing tools are thus subjected to greatly varying loads which depend upon the level to which the mixer is filled and the thickness of the layer of product above the submerged mixing tool. This produces considerable wear on the mixing tools and means that the mixing mechanism requires high power to operate it.